The indoor dead zone is the bane of wireless transmission. The higher the radio frequency, the shorter the wavelength and the easier it is for things like walls to stop signals cold. Actually, these impediments only attenuate or reduce them in power. But the effect is the same. Now you have a solid signal, now you don't. Satellite TV signals, which are at even higher frequencies than cellular, are easily blocked by even tree leaves or a good rainstorm.
One solution is to move to a lower frequency band. But there isn't much unused spectrum available and there already is a huge investment in the current cell tower network. AT&T and Verizon did snap up the 700 MHz TV channels that were recently auctioned. These frequencies have longer wavelengths and can penetrate buildings better. But even if these are pressed into service, what do you do with the hundreds of millions of phones and thousands of cellular base stations now in service?
Another solution is to increase transmission power to make signals go further. That won't work on the phone side because you really want less power, not more, to increase battery life. Well, how about just putting up more cell sites? Put one on every corner disguised as a street light. Hide them in the trees. Bring them inside and put them in the ceiling.
Wait! That's an idea. Why not bring the cell tower inside the building where the problem is? Not a full size one, of course. Just big enough to cover the dead zone. That's exactly what carriers have done in some cases. They'll install a small base station and antennas inside an office building and connect it to their network. Voila! Indoor cellular coverage. It's called a picocell to indicate its smaller size and coverage area.
Picocells could be the answer to all of our wireless coverage problem if they just weren't so expensive and labor intensive to install. If cellular towers could just create a miniature clone of themselves that resembled a WiFi router with a similar price and ease of installation...
Enter the femtocell. It's the Mini-Me of cell towers... sort of. Sprint is currently testing a femtocell called Airave in Indianapolis and Denver. If they like the results, there may be femtocells everywhere soon. Femtocells? Picocells? Where do they get these names?
Femto and pico are like micro and nano, only smaller. A pico something is one-thousandth of a nano. A femto is even smaller. It's a thousandth of a pico or a quadrillionth of the full deal. If you need to go even smaller, your next stops are atto, zepto and yocto. They'll probably implant yoctocells in your brain some day. Then you'll never get away from the yoc, yoc, yoctoing on the cell phone.
For now, the femtocell may come to your rescue in maintaining ubiquitous wireless communications. Sprint's Airave is more like WiFi router than you might think. It looks the part. Plus it connects to your broadband service through your existing router or Cable/DSL router.
Why the broadband connection? It's for backhaul. That's the connection to and from the phone company. The femtocell doesn't actually coordinate with the bigger cell towers. It's a stand alone device. You can't just keep talking as you walk through your front door. You have to hang-up and call back using the femtocell. Your Sprint cell phone communicates back and forth with the femtocell just like your notebook computer communicates with a WiFi router. The femtocell communicates back and forth with Sprint over your broadband service, just like you communicate with the Internet using a WiFi router.
This is more than just an analogy. Your calls go over the Internet similar to VoIP services. In a way, you have a combination of cellular and VoIP technology with all their advantages and limitations. The limitation on Internet for backhaul service is that call quality can be affected by network congestion on your broadband service and you lose service when you or your ISP loses power.
If you are going to have your calls go over the Internet, why not just skip the femtocell and use WiFi directly? That's what dual mode phones offer. T-Mobile is testing a service called HotSpot@Home that uses your wireless router instead of a femtocell. The key to this is a dual-mode cell phone that offers WiFi connections as one of the modes.
You could also use a wireless VoIP telephone handset and a service such as Skype to mimic femtocell service as a way to make inexpensive phone calls. But you'll have no coverage on the go. Once WiMAX or other wireless outdoor broadband coverage is available everywhere, wireless VoIP may give traditional cellular a run for its money. That is, unless the major cellular carriers, who now own the spectrum likely to be deployed for mobile broadband, decide to jump on this bandwagon themselves and all wireless phone services go IP instead of GSM or CDMA.
